Maxwell Render | Official public forum

Hi,

I have found this when I was trying to create a night scene. Following the link to the images.

http://min.us/mvb5r4

What happens is when I try to use an EXR/HDR mapped on a big mesh as sky (hemisphere) it affects the emitters on the scene. But if I applied the same EXR/HDR on a small mesh nothing wrong occurs.
Using the EXR/HDR on "Image Base Environment" is no good because you can not rotate the bitmap to position it the way you want. What I can do is to rotate all the objects, but it sounds bad to me.
Any sugestions?

I am using 3D Max 2011, Mawell 2.1.0.0 and Max plugin 2.1.1

Adriano

ps: In addition "Image Base Environment" do not permit to use the "Physical Sun" all together, isn't it? Again, if I want to use both types of illumination I must use a EXR/HDR mapped on a big mesh.

Half Life has noted how Maxwell seems to focus more on emitters with the most strength. That seems to be what is going on here. Your small 100w emitter would eventually get where it should be but the other emitter is so large (and probably very powerful, I'd guess) that Maxwell is using almost all resources to calculate THAT light source. The workaround that Half Life has suggested is to crank the value of your 100w emitter WAY up, tricking Maxwell into thinking it's just as important as your other emitter, then lowering the value in Multilight.

You can't combine illumination from IBL and Phys sky light sources within Maxwell. However you could export your phys sky as an .hdr/.exr and combine them in Photoshop and use your combined image for IBL. However, mixing a sunny hdr with a nightime hdr may give odd results so be warned.

-Brodie

Yep, Brodie is right, although I can't take credit for the lighting trick, that comes directly from Tom.

Also if you want to get a bit more juice out of your IBL you could consider modiying it via HDR Light Studio: http://www.hdrlightstudio.com/ Which can be a very nice tool to use with pre-existing IBL backgrounds.

Alternately you could output the physical sky as a HDR (or EXR) and composite with your IBL in something like Photoshop to juice it up manually.

Best,
Jason.

Hi,

thanks for your reply. I did some other tests considering your input. Yeah, it seems that size and intensity matters in this question. See next gallery.

http://min.us/mvgdmIr

First I reduced the sky (hemisphere) to 32 meters radius and EXR intensity to 0.1. The emitter 100W start to show up.
When I rescale the sky to 512 meters radius the emitter 100W weakens, and when I set the EXR intensity to 1.0 the emitter 100W weakens even more.
All sample level 8.

Adriano

The trick is to boost your emitter from 100W to more like 1000W before you render, and then dial it down with multilight back to what you feel is a realistic result.

The reason is Maxwell optimizes priority on stronger emitters, so you have to raise the power of the smaller emitter to compensate for the larger power of the EXR background to have them both render at the same speed.

If you let it render long enough it will all get to the same place, but you will have to render to higher SL to see the weaker emitter finish rendering.

Best,
Jason.

Got it!

Thanks,
Adriano

adrianoarquiteto wrote:Using the EXR/HDR on "Image Base Environment" is no good because you can not rotate the bitmap to position it the way you want. What I can do is to rotate all the objects, but it sounds bad to me.

You can rotate it using the offset and watch it rotate in real time either in the OpenGL viewport or with FIRE.

The old "sphere around the scene with reversed normals and HDR map applied" is not necessary. (And as you have found out, not efficient.)

Hi all,

Just a quick question, slightly off topic but still regarding emitters: Is it still recommended to weld together all meshes which
share the same emitter material? I have a scene with the physical sky + sun enabled, a few spot lights near the internal walls
and a few more florescent ceiling lights. At the moment all objects are separate 3dsMax standard primitives. So, is it better to
convert them all into meshes and then weld them?? I know this used to be the best way but I'm not sure how things have
changed in 2.5 for this matter.

Any quick advise is greatly appreciated! Cheers guys!

No longer necessary. That used to be the method to get multiple emitters on one ML slider. Now sliders are determined by the material (each emitter material gets 1 slider).

-Brodie

brodie_geers wrote:No longer necessary. That used to be the method to get multiple emitters on one ML slider. Now sliders are determined by the material (each emitter material gets 1 slider).

-Brodie

Cheers Brodie,
So it has no effect on light distribution, noise levels and therefore on render time anymore? How about using instances or real
copies, does that still make a difference? Thanks for your advise!

It's my understanding that those do not make a difference, although I've never personally tested it. Perhaps someone else could chime in but unless you here otherwise, I wouldn't be concerned with it.

I have a vague recollection of an error when trying to instance emitters but I could be thinking of something else.

In general instances don't affect render time, just voxelation time and memory usage during rendering. You shouldn't have so many emitters or such high poly emitters (number of polys in emitter geometry does affect render time) that either of those should be adding any noticeable time to voxelization nor should they be eating up much memory.

-Brodie

You cannot instance a mesh with an emitter material, nor can you assign an emitter material to an instance. Some plugins will handle this for you automatically, by just exporting geometry rather than an instance, when either of the above is the case.